Making the rake file for tests easier to read.

I'm defining a new class which modularizes how the `rake test` tasks are
defined and invoked.

railties/lib/rails/test_unit/sub_test_task.rb

@@ -2,13 +2,53 @@ require 'rake/testtask'
 
 module Rails
   class TestTask < Rake::TestTask # :nodoc: all
+    # A utility class which is used primarily in "rails/test_unit/testing.rake"
+    # to help define rake tasks corresponding to <tt>rake test</tt>.
+    #
+    # This class takes a TestInfo class and defines the appropriate rake task
+    # based on the information, then invokes it.
+    class TestCreator
+      def initialize(info)
+        @info = info
+      end
+
+      def invoke_rake_task
+        if @info.files.any?
+          create_and_run_single_test
+          reset_application_tasks
+        else
+          Rake::Task[ENV['TEST'] ? 'test:single' : 'test:run'].invoke
+        end
+      end
+
+      private
+
+        def create_and_run_single_test
+          Rails::TestTask.new('test:single') { |t|
+            t.test_files = @info.files
+          }
+          ENV['TESTOPTS'] ||= @info.opts
+          Rake::Task['test:single'].invoke
+        end
+
+        def reset_application_tasks
+          Rake.application.top_level_tasks.replace @info.tasks
+        end
+    end
+
+    # This is a utility class used by the <tt>TestTask::TestCreator</tt> class.
+    # This class takes a set of test tasks and checks to see if they correspond
+    # to test files (or can be transformed into test files). Calling <tt>files</tt>
+    # provides the set of test files and is used when initializing tests after
+    # a call to <tt>rake test</tt>.
     class TestInfo
       def initialize(tasks)
         @tasks = tasks
+        @files = nil
       end
 
       def files
-        @tasks.map { |task|
+        @files ||= @tasks.map { |task|
           [task, translate(task)].find { |file| test_file?(file) }
         }.compact
       end
@@ -53,8 +93,9 @@ module Rails
       end
     end
 
-    def self.test_info(tasks)
-      TestInfo.new tasks
+    def self.test_creator(tasks)
+      info = TestInfo.new(tasks)
+      TestCreator.new(info)
     end
 
     def initialize(name = :test)

railties/lib/rails/test_unit/testing.rake

@@ -7,18 +7,7 @@ task default: :test
 
 desc 'Runs test:units, test:functionals, test:integration together'
 task :test do
-  info = Rails::TestTask.test_info Rake.application.top_level_tasks
-  if info.files.any?
-    Rails::TestTask.new('test:single') { |t|
-      t.test_files = info.files
-    }
-    ENV['TESTOPTS'] ||= info.opts
-    Rake.application.top_level_tasks.replace info.tasks
-
-    Rake::Task['test:single'].invoke
-  else
-    Rake::Task[ENV['TEST'] ? 'test:single' : 'test:run'].invoke
-  end
+  Rails::TestTask.test_creator(Rake.application.top_level_tasks).invoke_rake_task
 end
 
 namespace :test do